Medical diagnostic imaging and scanning machines such as magnetic resonance imaging (MRI) apparatus, X-ray machines, positron emission tomography (PET) scanners, and computer tomography (CT) scanners are well known. Such machines are quite popular as a tool for diagnosis of tumors and the like. Owing to good quality tomographic images with low dosage X-ray radiation, the CT scanner has become especially well accepted by the medical profession.
An annular gantry normally supports many of the components of a CT scanner and includes an outer ring secured to a stand and an inner ring mounted for rotation within the outer ring. During a scanning procedure, a patient table is positioned through the center of the gantry and the inner ring is rotated about the table. The components supported by the gantry can include an x-ray tube for providing the x-ray beam, one or more high voltage power supplies, balancing weights, a data acquisition module, and a bank of detectors diametrically opposed from the x-ray source. At least some of these components are secured in the inner ring for rotation therewith.
In order to obtain tomographic images of a patient with a CT scanner or X-ray CT apparatus, it is necessary that the patient be located exactly at a predetermined position inside the opening of an annular scan gantry of the apparatus. For this reason, such apparatus has been provided with a patient handling couch or table which is moveable vertically to be in line with an axis of the scan gantry, and moveable axially in and out of the scan gantry. Several patient tables are known for this purpose.
Patient positioning systems are used for accurate and reproducible positioning of a patient for radiation therapy, diagnostic imaging, surgery, and other medical procedures. During these procedures, it is important to immobilize a part or parts of the patient's body. Accurate positioning of the body part is also important in repeat treatments so that the precise same location of the bodies are exposed to the radiation each time. Therefore, different types of devices have been made to immobilize body parts and to index the body to the treatment table to assure proper and repeatable alignment for radiation therapy.
One example of such a patient positioning system is described in U.S. Pat. No. 5,806,116. The positioning system utilizes a tabletop with indentations, or notches, along opposite sides, and a lock bar extending across the tabletop with a disk at each end adapted to be received in opposing indentations. The lock bar is secured to the tabletop with an eccentric cam which tightens the ends of the bar into engagement with the indentations of the tabletop.
Another patient positioning system is described in U.S. Pat. No. 6,161,237, which shows a table having opposite sides with indexing notches along each side. A patient restraint member is registered on an elongated lock bar and is adapted to extend over a portion of the patient's body to position the patient on the table. The lock bar has a downwardly extending circular ball on each end adapted to snap-fit into opposing pairs of the notches on each side of the table.
What is still desired is a new and improved patient positioning system for radiation therapy treatment. Preferably the new and improved system will not rely upon using notches in a patient table, such that the table is easier and less expensive to manufacture and can be repaired if damaged.